DRAGONFLIES AND DAMSELFLIES IN PONDFISH CULTURE. 211 
7. ALGH, FUNGI, AND VoRTICELLIDS.—‘‘The Confervoid alga, Cidogonium, is 
often found growing upon the larva of 4schna brevistyla. I found by means of sections 
that the Cidogonium does not penetrate the cuticle of the larva, but simply grows 
on it as it grows on everything else in such places. On one larva of A/schna there were 
no less than 3 species of Cdogonium, 15 species of Diatoms, and a large number of 
Vorticella.”” (Tillyard, 1917, p. 332.) (&dogonium is very common in several of the 
ponds at Fairport and is found growing over many of the pond contents, including 
nymphs, but it appears to do them no injury further than to impede their movements 
slightly. 
Miss Lyon (1915, p. 5) published a table giving the Diatoms, green and blue-green 
algz, the protozoa, and the epizoa found growing upon the nymphs of Cascadilla Creek 
She noted the similarity between these species and those of the mud and water plants 
in the immediate vicinity. She concluded that the relationship between the two was 
simply a natural one, resulting from the proximity of the various forms, and not one of 
symbiosis, as Kammerer and others would have us believe. 
Similarly a Saprolegnious fungus frequently attacks damselfly nymphs, especially 
if they are enfeebled from any cause. This fungus is related to the one attacking 
young fishes and often causes the death of the nymph. (Garman, 1917, p. 442.) 
8. Brrps.—Needham has recorded dragonfly nymphs as found in considerable 
numbers in the stomachs of herons (1898, p. 85). McAtee (1912) also recorded nymphs 
as forming part of the food of the horned grebe, Colymbus auritus. But herons and grebes 
and their kin are deadly enemies of fish, and hence should always be kept away from 
fishponds. Under natural conditions, however, they might well consume a considerable 
quantity of nymphs. 
9. REPTILES.—Martin (1886, p. 232) said with reference to the Odonata of the 
Départment de 1’Indre in France: 
The eggs, larve, and nymphs are the prey of several fishes, snakes, newts, Coleoptera, aquatic 
Hemiptera, and of some diving birds. Sometimes the destruction is on a considerable scale, and one 
may notice the dragonflies of some piece of water diminish gradually in numbers, while the animals 
that prey on them increase, so that a species may for a time entirely disappear in a particular spot, 
owing to the attacks of some enemy that has been specially prosperous and also eager in their pursuit. 
Baker (1906, pp. 231, 232) in his study of The Relation of Mollusks to Fish in 
Oneida Lake found numerous dragonfly nymphs in the stomachs of painted terrapins, 
Chrysemys picta. 
None of the terrapin at Fairport were examined for the food they had eaten, but 
they may fairly be reckoned among the enemies of the nymphs. 
Ordinarily the dragonfly nymph is able to hold its own in spite of its enemies, 
and it requires conditions exceptionally adverse to the nymph and exceptionally 
favorable to its foes before there is any danger of the extermination of the nymphs. 
FOOD OF ODONATE IMAGOS. 
There are several things which make it difficult to obtain specific lists of the food 
of the imagos similar to those presented for the nymphs. 
A considerable portion of the animals eaten by the nymphs, such as snails, ento- 
mostraca, beetles, hemiptera, and the like, are inclosed in hard shells or elytra, which 
persist inside the digestive canal of the nymph and are easily recognized. The food 
